Quick answer: Fat makes up most of the calories on keto, commonly around 60–80% of calories, because the body needs a steady supply of fatty acids to make ketones once carbs are low. Your exact needs depend on calories, activity and goals. Emphasize unsaturated fats such as olive oil, avocado, nuts and fatty fish, and keep an eye on cholesterol with your provider.
Key takeaways
With carbohydrates restricted, fat becomes the main fuel and the raw material for ketones.
Fat fills the calories left over after protein and carbohydrates, and too much protein or carbohydrate can make ketosis harder.
Favoring olive oil, avocado, nuts, seeds and fatty fish matters because LDL cholesterol rises in some people on keto.
Why fat is so high
With carbohydrates restricted, fat becomes the main fuel and the raw material for ketones. See what is ketosis.
How much fat?
Fat fills the calories left after protein and carbs. Use the keto macro calculator. These ranges are general education, not a prescription; your needs depend on your health, medications and goals, so personalize them with your provider.
Balancing your macros
Too much protein or carbohydrate can make ketosis harder. See moderate protein and low carbohydrate intake.
Choosing quality fats
Choose olive oil and avocado oil, avocados, nuts and seeds, and fatty fish such as salmon and sardines, with moderate amounts of butter, ghee and coconut oil. Avoid trans fats and limit fried and processed foods. You can find the full list in keto fat foods.
Healthy aging lens
Some people see LDL cholesterol rise on keto. Checking a lipid panel before and after starting, and favoring unsaturated fats, is a sensible precaution for heart health.
What the research shows
High-fat, low-carbohydrate eating has been tested against higher-carbohydrate diets in controlled settings.
Keto under tightly controlled conditions (Hall 2016, metabolic ward study). 17 men with overweight or obesity lived on a research ward, eating a high-carbohydrate diet for 4 weeks and then a ketogenic diet with the same calories and protein for 4 weeks. Energy use rose a little on keto (about 57 to 151 kcal a day depending on the method), but body fat loss actually slowed, while loss of lean mass increased. A limitation is that there were only 17 men, the diets were not randomized in order, and 4 weeks may be too short to see longer-term adaptation.
Animal-based keto vs. plant-based low-fat (Hall 2021, inpatient randomized crossover trial). 20 adults lived at the NIH Clinical Center and ate a minimally processed, animal-based ketogenic diet (about 76% fat) and a minimally processed, plant-based low-fat diet for 2 weeks each, eating as much as they wanted. They ate about 689 kcal a day less on the low-fat diet, although they lost weight on both diets. A limitation is the short 2-week periods; one participant also withdrew due to low blood sugar on the ketogenic diet.
Keto vs. low-fat over a year or more (Bueno 2013, meta-analysis of 13 randomized trials). This review pooled trials lasting at least 12 months that compared a very-low-carbohydrate ketogenic diet (50 g of carbohydrate a day or less) with a low-fat diet in 1,415 adults. The keto groups lost about 0.9 kg more, had lower triglycerides and slightly lower diastolic blood pressure, and had higher HDL cholesterol. They also had higher LDL cholesterol (about 0.12 mmol/L). A limitation is that the average extra weight loss was small, and people in these trials often drifted away from strict keto over time.
Strength of the evidence: Controlled studies suggest high fat intake does not by itself speed fat loss, and LDL cholesterol rises in some people, so fat quality matters.
When to see a naturopathic doctor
It may be time to see a naturopathic doctor if you have diabetes or take insulin, sulfonylureas or SGLT2 inhibitors (risk of low blood sugar or ketoacidosis), or if you take blood pressure medication or diuretics. The same is true if you have kidney, liver, gallbladder or pancreas disease, or high cholesterol, if you are pregnant, breastfeeding, or have a history of disordered eating, or if you want a keto plan tailored to your labs and goals.
See a medical provider promptly for nausea and vomiting, abdominal pain, confusion, fruity-smelling breath with rapid breathing, or very high blood sugar or ketone readings, which can signal ketoacidosis.
Want a keto plan that’s safe for your health?
A free 15-minute consultation with Dr. Kneessi. No cost, no obligation. In-office in Odenton, MD or by telehealth.
Questions to bring to your clinician
These questions can help you get the most out of your next visit.
Should we check my lipid panel before and after I start eating more fat on keto?
Which fats should make up most of my diet on keto?
Should I be watching my cholesterol more closely on a high-fat diet?
How can I keep fat intake high without relying on processed foods?
Frequently asked questions
Why is keto so high in fat?
Fat becomes the main fuel and is used to make ketones.
How much fat should I eat on keto?
It varies; fat typically fills the remaining calories after protein and carbs.
Can keto raise cholesterol?
In some people, yes. Check a lipid panel with your provider.
What are the best fats?
Olive oil, avocado, nuts, seeds and fatty fish.
Sources
- Anderson JC, et al. Measuring ketone bodies for the monitoring of pathologic and therapeutic ketosis. Obes Sci Pract 2021. PMID: 34631141. https://pmc.ncbi.nlm.nih.gov/articles/PMC8488448/
- Swanson D, Block R, Mousa SA. Omega-3 fatty acids EPA and DHA: health benefits throughout life. Adv Nutr 2012. PMID: 22332096. https://pmc.ncbi.nlm.nih.gov/articles/PMC3262608/
- Retterstøl K, et al. Effect of low carbohydrate high fat diet on LDL cholesterol and gene expression in normal-weight, young adults: A randomized controlled study. Atherosclerosis 2018. PMID: 30408717. https://pubmed.ncbi.nlm.nih.gov/30408717/
- Sacks FM, et al. Dietary Fats and Cardiovascular Disease: A Presidential Advisory From the American Heart Association. Circulation 2017. PMID: 28620111. https://pubmed.ncbi.nlm.nih.gov/28620111/
- MedlinePlus: Dietary Fats
- MedlinePlus: Cholesterol
- Hall KD, et al. Energy expenditure and body composition changes after an isocaloric ketogenic diet in overweight and obese men. Am J Clin Nutr 2016. PMID: 27385608. https://pubmed.ncbi.nlm.nih.gov/27385608/
- Hall KD, et al. Effect of a plant-based, low-fat diet versus an animal-based, ketogenic diet on ad libitum energy intake. Nat Med 2021. PMID: 33479499. https://pubmed.ncbi.nlm.nih.gov/33479499/
- Bueno NB, et al. Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials. Br J Nutr 2013. PMID: 23651522. https://pubmed.ncbi.nlm.nih.gov/23651522/
This article is for educational purposes only and is not medical advice. It does not replace an individual evaluation. Talk with your healthcare provider before starting supplements or changing medications, especially if you are pregnant, nursing, or managing a health condition.
Free: The 28-Day Reset for Energy and Focus
A simple day-by-day email guide to sleep, movement, food, and daily habits that support healthy aging. It’s free, and you can unsubscribe anytime.
Get the free guide Take the supplement quiz
